1. Field of the Invention
The invention relates to a method for manufacturing a screen cylinder, in which method screen wires are set at predefined intervals side by side and fastened in the axial direction of the screen cylinder to form a cylindrical screen surface in connection with ring-shaped support rods, and in which method end rings are further mounted at the ends of the screen cylinder.
The invention further relates to a method for manufacturing a screen cylinder, in which method screen wires are set at predefined intervals side by side and fastened to support rods that are bent in the shape of a ring so that the screen wires in the axial direction of the screen cylinder form a cylindrical screen surface, and in which method end rings are further mounted at the ends of the screen cylinder.
The invention yet further relates to a screen cylinder for cleaning or screening fiber pulp, the screen cylinder having screen wires in the axial direction of the screen cylinder set at predefined intervals to form a cylindrical screen surface and fastened to ring-shaped support rods, and the screen cylinder ends having end rings arranged thereto.
2. Description of Related Art
Screen cylinders are used for instance to clean and screen fiber pulp. Screen cylinders are manufactured for instance by fastening parallel screen wires that form a screen surface side by side in a cylindrical form so that a slot of a desired size remains between the wires. Generally this is done by welding or brazing the screen wires to ring-shaped support wires or rods. The screen wires can be fastened to the support rods in the radial direction of the screen cylinder either inside or outside the support rods. To strengthen the structure of the screen cylinder, separate support rings can be fastened to at least a few of the ring-shaped support rods. These support rings are fastened either to the inner circumference or outer circumference of the support rods depending on the relative order of the screen wires and support rods in the radial direction of the screen cylinder. The structure of the screen cylinder is complemented by fastening end rings at the ends of the screen cylinder. When the end rings are fastened to the ends of the screen cylinder, the ends of the screen wires are welded to the end rings.
However, fastening the end rings by welding causes a lot of work, first when opening the root of the weld and, after that, during the actual welding. For instance, in a screen cylinder with a diameter of 1200 mm, over 20 meters of weld joint is produced. Fastening the end rings to the screen cylinder by welding also causes welding stresses in the structure of the screen cylinder, whereby during use loads are generated due to the varying pressure inside the screen and mechanical loads, and the generated loads may make the structure of the screen cylinder break.